Millions of pounds have been spent in the last 10 years on improvements to road bridges to ensure they can cope with loading from heavy vehicles. Faced with complex and expensive repairs to a 110-year-old viaduct, however, Leicester City Council has chosen a different solution – demolition of the entire bridge.
The Upperton Road Viaduct in the south west of the city was originally built between 1896 and 1899 to carry the Upperton Road over the Great Central Railway and the Old River Soar. The road has since become one of the city's main east/west links, carrying up to 20,000 vehicles a day, but the viaduct was never designed to carry 21st century traffic loads, and its condition has increasingly been of concern to the authority.
The council has opted to replace the structure with a new, low-level road built on the same alignment. The only section of bridge on the new road will be a single-span structure over the river.
Knocking the viaduct down will help the council to tackle crime and security problems in the surrounding area, much of which is derelict.
The new scheme will open up the area and link it to key regeneration areas in the city.
The project is possible primarily because in 1969 trains stopped running on the track, which passes under the viaduct. The section near Upperton Road is now part of the Great Central Way, a 16km pedestrian and cycle route through the city that is part of the National Cycle Route. With the railway line gone, much of the viaduct is redundant.
The new road will, for the most part, follow the contours of the original, sloping down quite steeply from the west side to cross the river. However, extensive retaining walls will be needed at the west end to support buildings erected at the higher level.
Leicester City Council appointed Jacobs as designer for the £18M scheme, which is being funded by the Department for Transport. It gave Nuttall an £11M contract for the construction on an early contractor involvement (ECI) basis, with the contractor contributing to design and buildability issues.
Work began on site in May 2007, with the first five months focused on building a temporary diversion road so that traffic could be taken off the existing route. This road was built in two halves, leaving a gap in the middle that could only be completed once the viaduct was demolished.
Construction had to be completed by October, when Nuttall had arranged permission for a nine-day closure of the Upperton Road to demolish the bridge and build the final section of the diversion road.
The temporary road includes three bridges, one taking vehicles and two carrying pedestrians over the river.
Access to the site is very limited, and Nuttall realised it would be almost impossible to get a crane into position to lift the temporary road bridge into place. Instead, the Mabey-supplied 35m x 7.3m bridge was built in stages on the old railway sidings on one side of the river and launched across.
The road closure itself was booked to coincide with school half term. The old Upperton Road was closed at 8pm on Friday 19 October, and the temporary road opened at 8am on Monday 26 October.
"Beforehand, we produced a programme for the nine days and got everyone in a couple of days earlier so that all the companies involved knew what they were doing and when they had to come in and do their work," explains Nuttall's sub-agent Dave Lewis. "We had predefined dates within that nine days."
The old viaduct was built using brick arch construction for spans at the end and the remaining 10 central spans built on steel trestles with a deck that consisted of steel girders with a steel deck plate on top. Demolition involved cutting the deck between the girders to separate them, and then lifting the trestles off their foundations.
During the nine-day closure, 7,000t of brickwork was taken down, 8,000t of road surfacing planed out, 748t of steel dismantled and 1,840t of material (in the form of acceptable fill and hardcore) taken away. Nuttall also laid 200t of wearing course and 440t of base course.
The only section of the viaduct not to come down during the October closure was the brick arch spanning the Old River Soar. Its original deck had been waterproofed using a form of coal tar, which must be removed under controlled conditions before the structure is taken down to ensure that there is no contamination of the river.
Nuttall intends to have this demolition complete at the end of this month and then it will get on with construction of the new river crossing, a 30m, single span composite bridge deck built on the abutments of the original viaduct structure. "Building on the old abutments means there is none of the usual risk [of trying to excavate cold, hard ground] when you're doing foundations in winter weather," explains Lewis.
The new deck beams will be lifted into position using an 800t mobile crane positioned on the west abutment. "The beams will be lifted in pairs, and we'll do as much preparation work as possible before the lifts to limit working at height and working over water," says Lewis.
Work has already started on the retaining wall at the west end of the 380m long stretch of new, permanent road. It will be faced with some of the 33,000 engineering bricks rescued from the viaduct demolition, with the remainder going on the wing walls and abutments of the new river bridge.
Traffic is due to be switched to the permanent road in September, after which Nuttall has three months to remove the temporary road and landscape the scheme.
Upperton Road's revival - step by step
1. A temporary road layout takes traffic off the viaduct so it can be demolished
2. The diversion road includes three temporary bridges
3. The viaduct was demolished in just nine days
4. Work has now started on retaining walls using bricks rescued from the demolition
5. PROJECT DETAILSProject: Upperton Road Viaduct Redevelopment
Client: Leicester City Council
Project cost: £18.2M
Construction cost: £11M
Construction period: May 2007 – December 2008
Funding: Department for Transport The final section of viaduct is taken down under controlled conditions